The structural and functional state of chromatin during the cell division cycle will be investigated in synchronized cultures of tumor cells. Part of the study will concern the regulation of RNA synthesis during mitosis, and the mechanisms by which the transcriptions of individual RNA species are controlled independently of one another at this time. A second portion of the investigation will deal with changes in the intranuclear organization of interphase chromatin, as measured by its capacity to bind various DNA ligands, particularly H3-actinomycin. The chemical and physical alterations of DNA or chromosomal proteins which underly chromatin binding changes during the cell cycle will also be investigated.